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1.
The aim of this research was to assess the efficiency of Fenton’s oxidation for degradation of endocrine disruptor bisphenol A (BPA) with emphasis on extent of accompanying adsorption. Adsorption on the waste sludge resulting from the Fenton’s oxidation could represent a significant impact on the final removal efficiency of BPA. Fenton’s oxidation was accomplished at two concentrations of BPA (0.228 and 22.8 mg L?1); both at the selected molar ratio of reagents Fe2+:H2O2 (1:10), as a function of reaction time. The kinetics of adsorption of BPA on waste sludge was determined for the same two concentrations of BPA at two concentrations of waste sludge (0.1 and 6.0 g L?1). In addition to changing concentrations of BPA and sludge, the adsorption process was also influenced by parameters such as temperature, pH and contact time. Adsorption isotherms were determined. Oxidation and adsorption were monitored by gas chromatography combined with mass spectrum. It has been confirmed that BPA is not completely oxidized in Fenton’s oxidation, because it is adsorbed to formed waste ferric sludge and thus necessary precautions for sludge deposition must be observed.  相似文献   

2.
Sludge samples taken from different sources and times may have different characteristics that could affect dewatering performance. In this study, 20 sludge samples from five wastewater treatment plants and different seasons in 1 year were characterized. Pearson correlation analysis indicated that solid content (SC), total suspended solid (TSS), polysaccharides and proteins contents had positive correlations with the capillary suction time (CST), whereas volatile suspended–solid/total suspended solid (VSS/TSS) exhibited negative correlations with CST. Moreover, no correlations between CST and specific resistance to filtration were found among these different sludge samples. The principal component analysis confirmed that only two group variables could represent most of the sludge characteristic parameters. The first set of variables represents the particulate nature of the biotic factors (SC, VSS/TSS, SCOD, TSS, polysaccharides and proteins), and the second set is the pH. CST could not be a reasonable indicator of dewaterability in sludge deep dewatering by Fe2+/S2O8 2?-phosphogypsum composite conditioning. Furthermore, the results of diaphragm filter press dewatering showed that initial SC and VSS/TSS were the most dominant sludge characteristics affecting the solid content of dewatered cake (R p = 0.610, p = 0.016; R p = ?0.838, p = 0.000, respectively) with Fe2+/S2O8 2?-phosphogypsum composite conditioning. Results from this study suggest that dewatering performance is predictable by sludge characteristics parameters for Fe2+/S2O8 2?-phosphogypsum conditioning.  相似文献   

3.
δ 13C values of crop and forest soils were measured 8 years after disposal of paper sewage sludge. The carbon transfer from paper sludge downward to the first humic layer is evidenced by a 13C-enrichnient of up to + 5.6‰ due to the input of 13C-enriched sludge carbonates. 13C/12C composition is thus a novel, sensitive parameter to follow the downward transfer of paper sludge carbon.  相似文献   

4.
The novel coronavirus, SARS-CoV-2, which has caused millions of death globally is recognized to be unstable and recalcitrant in the environment, especially in the way it has been evolving to form new and highly transmissible variants. Of particular concerns are human-environment interactions and the handling and reusing the environmental materials, such as effluents, sludge, or biosolids laden with the SARS-CoV-2 without adequate treatments, thereby suggesting potential transmission and health risks. This study assesses the prevalence of SARS-CoV-2 RNA in effluents, sludge, and biosolids. Further, we evaluate the environmental, ecological, and health risks of reusing these environmental materials by wastewater/sludge workers and farmers. A systematic review of literature from the Scopus database resulted in a total of 21 articles (11 for effluents, 8 for sludge, and 2 for biosolids) that met the criteria for meta-analysis, which are then subdivided into 30 meta-analyzed studies. The prevalence of SAR-CoV-2 RNA in effluent and sludge based on random-effect models are 27.51 and 1012.25, respectively, with a 95% CI between 6.14 and 48.89 for the effluent, and 104.78 and 1019.71 for the sludge. However, the prevalence of SARS-CoV-2 RNA in the biosolids based on the fixed-effect model is 30.59, with a 95% CI between 10.10 and 51.08. The prevalence of SARS-CoV-2 RNA in environmental materials indicates the inefficiency in some of the treatment systems currently deployed to inactivate and remove the novel virus, which could be a potential health risk concern to vulnerable wastewater workers in particular, and the environmental and ecological issues for the population at large. This timely review portends the associated risks in handling and reusing environmental materials without proper and adequate treatments.  相似文献   

5.
Cadmium and zinc were added at 3 and 300 mg kg−1, respectively, to 23 soils and incubated at 16°C and 80% field capacity for 818 d. Following addition of metal, changes in the radio-labile concentrations of both elements were examined on seven separate sampling occasions over 818 d. At each sample time, soil pore water was extracted using Rhizon soil solution samplers, and concentrations of Cd, Zn, dissolved organic carbon, and major cations and anions were determined. The chemical speciation program WHAM 6 was used to determine free metal ion activity, (M2+). Similar measurements were made on a set of historically contaminated soils from old mining areas, sewage sludge disposal facilities, and industrial sources. The two data sets were combined to give a range of values for p(Cd2+) and p(Zn2+) that covered 5 and 4 log10 units, respectively. A pH-dependent Freundlich model was used to predict Zn2+ and Cd2+ ion activity in soil pore water. Total and radio-labile metal ion concentration in the solid phase was assumed to be adsorbed on the “whole soil,” humus, or free iron oxides to provide alternative model formats. The most successful models assumed that solubility was controlled by adsorption on soil humus. Inclusion of ionic strength as a model variable provided small improvements in model fit. Considering competition with Ca2+ and between Zn2+ and Cd2+ produced no apparent improvement in model fit. Surprisingly, there was little difference between the use of total and labile adsorbed metal as a model determinant. However, this may have been due to a strong correlation between metal lability and pH in the data set used. Values of residual standard deviation for the parameterized models using labile metal adsorbed on humus were 0.26 and 0.28 for prediction of p(Cd2+) and p(Zn2+), respectively. Solubility control by pure Zn and Cd minerals was not indicated from saturation indices. However there may have been fixation of metals to non-radio-labile forms in CaCO3 and Ca-phosphate compounds in the soils in the higher pH range. Independent validation of the Cd model was carried out using an unpublished data set that included measurements of isotopically exchangeable Cd. There was good agreement with the parameterized model.  相似文献   

6.
Quantum mechanical calculations based on the density functional theory (DFT) are used to study the crystal structures of dioctahedral 2:1 phyllosilicates. The isomorphous cation substitution is investigated by exploring different substitutions of octahedral Al3+ by Mg2+ or Fe3+, tetrahedral substitution of Si4+ by Al3+, and different interlayer cations (IC) (Na+, K+, Ca2+, and Mg2+). Samples with different kinds of layer charges are studied: only tetrahedrally charged, only octahedrally charged, or mixed octahedral/tetrahedral charged. The effect of the relative arrangements of these substitutions on the lattice parameters and total energy is studied. The experimental observation of segregation tendency of Fe3+ and dispersion tendency of Mg2+ in the octahedral sheet is reproduced and explained with reference to the relative energies of the octahedral cation arrangements. These energies are higher than those due to the IC/tetrahedral and IC/octahedral relative arrangements. The tetrahedral and octahedral substitutions that generate charged layers also tend to be dispersed. The octahedral cation exchange potentials change with the IC-charge/ionic radius value.  相似文献   

7.
Electrical properties of natural alexandrite (BeAl2O4:Cr3+) are investigated by the thermally stimulated depolarization current (TSDC) technique. Samples are submitted to consecutive annealing processes and TSDC is carried out after each annealing, yielding bands with different parameters. These bands are fitted by a continuous distribution of relaxation parameters: activation energy and pre-exponential factor of the Arrhenius equation. It has been observed that annealing influences the dipole relaxation behavior, since it promotes a modification of Fe3+ and Cr3+ impurity distributions on sites of distinct symmetry: Al1 and Al2. In order to have a reference for comparison, TSDC is also carried out on a synthetic alexandrite sample, where the only impurity present is Cr3+ ion.  相似文献   

8.
The partitioning of Gd in the experimental system diopside-aqueous vapor as a function of temperature, pressure, composition of the phases, time, grain size, solid-liquid ratio and Gd concentration has been investigated. A radioactive tracer measurement was used to determine Gd concentration in the separated phases. Diposides were reacted with aqueous vapor containing tracer Gd and reversibility was tested by reacting Gd-doped diopsides with pure aqueous vapor. Equilibration of Gd between the bulk of the diopside and the liquid was found to be limited by the slow rate of Gd diffusion in diopside, maximum value of D = 2 × 10?15cm2sec?1 at 800°C and 1 kb. Depending on whether the diopside was previously synthesized or synthesized from an oxide mix during the experiment, Gd concentrations were zoned in the crystal such that higher concentrations existed at the edges or center, respectively. Equilibrium is difficult to achieve in these experiments, but at the optimum experimental conditions for equilibration, the Gd diopside-aqueous vapor distribution coefficient is 20 ± 6 (800°C, 1 kb) in approximate agreement with previous results of 55 ± 23. Changing the composition of the aqueous vapor indicated that possible mechanisms for Gd substitution included coupling of Gd3+ with H+ or Na+ replacing 2Ca2+, or substitution of 2Gd3+ for 3Ca2+ with formation of a cation vacancy.  相似文献   

9.
This paper presents an experimental study on a deeply dewatered sewage sludge produced by using a new technique of membrane filter press. The experiments involve measurements of sludge composition, basic physical properties, shear strength, water permeability, and leaching toxicity. The measurements of shear strength and permeability were also performed on the sludge specimens soaked in a low acid leachate or distilled water for 1 and 2 months. This is to investigate the influence of chemical change in pore fluid as a result of rainfall infiltration or leachate seepage at landfills. Comparison tests were also carried out on silty clay that is commonly used for landfill cover material. The experimental results show that the deeply dewatered sludge contains 66 % organic content and 85 % water content (dry mass basis). The undrained shear strength of the sludge is >25 kPa even after 2-month soaking in the leachate and distilled water, meeting the requirement of the Chinese standard [CJ/T249-2007, Disposal of sludge from municipal wastewater treatment plant: sludge quality for co-landfilling. Ministry of Building and Construction, P.R. China (in Chinese), 2007]. The measured cohesion and friction angle for the sludge are >20 kPa and 22.3°, respectively. The soaking of sludge specimens in either leachate or distilled water resulted in an increase in frictional angle by several degrees. The water permeability for the sludge ranges from 0.68 × 10?8 to 1.3 × 10?8 cm/s, and permeability after 2-month soaking is less than the minimum requirement for the barrier layer of landfill covers (i.e., 1.0 × 10?7 cm/s). The concentrations of heavy metals leaching from the dewatered sludge are lower than the limit values of leaching toxicity for the wastewater discharge standard of China. The experimental results indicate that deeply dewatered sludge can be used as an alternative material for the barrier layer of landfill covers.  相似文献   

10.
The transformation of vivianite and the direct synthesis starting from pure chemicals lead to the formation of lipscombite {Fe x 2+ Fe 3?x 3+ [(OH)3?x/(PO4)2]} with varying Fe2+/Fe3+ molar ratios. The influence of this ratio on the Mössbauer spectra, solubility, electrokinetic potential and infrared spectra has been studied. By means of Mössbauer spectroscopy, the distribution of the Fe2+ and Fe3+ ions between the octahedral sites I and II has been investigated. The unit cell dimensions have been determined from Guinier-Hägg X-ray diffraction patterns. The crystal system is tetragonal for synthetic lipscombite with a=5.3020±0.0005 Å and c=12.8800±0.0005 Å. Lipscombite has been found to show a negative and time-dependent zeta-potential which, moreover, is influenced by the pH of the suspension and the Fe2+/Fe3+ molar ratio. An explanation of the time-dependence of the zeta-potential on variations of solubility is proposed. Infrared absorption spectrum only is characterized by two absorption bands: v OH(3,500 cm?1) and v P?O(1,100-960 cm?1). The density at 25° C is determined in toluene as 3.36±0.01 g·cm?3.  相似文献   

11.
The atmospheric levels of carbon dioxide (CO2) and other greenhouse gases (GHGs) have increased dramatically since the industrial revolution. The atmospheric enrichment with CO2 and other GHGs has resulted in multiple negative consequences: such as the increase in the average temperature and the rise of the sea level. Hence, there is a growing interest in developing feasible methods to reduce the atmospheric levels of these gases. One of these strategies is to enhance C sequestration through the increase of soil organic carbon (SOC) pool by the amendment of agricultural soils with sewage sludge. However, there is considerable uncertainty about the effects (positive or negative) of sewage sludge applications on the SOC pool. Thus, a simple approach developed under laboratory conditions is presented to discern the effect of a single sewage sludge application of 50 t ha−1 on the short-term SOC pool in 60 contrasting agricultural soils. The role of soil factors in the C sequestration of the recently added carbon was also studied. The application of sewage sludge supposed a mean increase of 1.7 ± 1.6 g SOC kg−1, with peak increases of up to 3.8 g SOC kg−1 and decreases of up to 4.6 g SOC kg−1. The initial SOC contents conditioned the C sequestration after sewage sludge application, and no other soil property was related.  相似文献   

12.
《Chemical Geology》2006,225(3-4):314-321
Calcite crystals were grown in the presence of small concentrations (50, 200, and 600 ppm) of divalent cations (Ba2+, Sr2+, Co2+ and Mn2+) in a silica hydrogel medium. The calcite crystals grown in the presence of cations larger than Ca2+ (Ba2+ or Sr2+) developed rhombohedral habits defined by {101¯4} form, similar to the morphology of calcite grown in a pure gel. SEM images show that growth on {101¯4} occurs by lateral advancement of layers bounded by macroscopic dendritic or jagged steps. In the case of calcite crystals grown in a gel doped with cations smaller than Ca2+ (Co2+ or Mn2+), a variety of morphologies was obtained, ranging from blocky crystals (at lower concentrations: 50 and 200 ppm) to peanut-like aggregates, spheres and spherulites (at 600 ppm). The macroscopic morphological characteristics of such doped calcite crystals reflect closely the growth behaviour of calcite {101¯4} surface at a nanoscale, reported by previous AFM studies. Morphological features have been interpreted on the basis of the modification of growing steps characteristics as a consequence of asymmetrical cation incorporation. The use of such morphologies as a criterion of biological activity is, therefore, unreliable.  相似文献   

13.
The adsorption and desorption behaviors of 17??-ethinylestradiol on various sludges derived from different treatment units of a sewage treatment plant were investigated using batch equilibration experiments. The results showed that adsorption process could be well described by pseudo-second-order kinetic model and fast adsorption played a main role. Adsorption ability varied as the order of aerobic sludge????anoxic sludge????primary sludge?>?sludge cake?>?anaerobic sludge. Adsorption/desorption isotherms were well fitted by the modified Freundlich model, and $ K_{f}^{\prime } $ values increased with the organic matter content. Thermodynamic analysis indicated that 17??-ethinylestradiol adsorption/desorption was exothermic and conducted spontaneously. After heat treatment for removing the organic carbon, $ K_{f}^{\prime } $ values decreased by more than 78%, but organic carbon normalized adsorption constant was 7.76?C29.51?mg/g. The 17??-ethinylestradiol adsorption capacity was found to decrease from 0.95?C1.39 to 0.44?C0.49?mg/g with sludge concentration increasing from 500 to 4,000?mg/L, being almost unchanged at pH 3?C10 and sharply decreasing with pH?>?10. The adsorption capacity was also found to fluctuate in the range of 2.0?C3.0?mg/g when Ca2+ concentration was <0.5?mol/L and increased rapidly above 0.5?mol/L. Addition of methanol and acetonitrile could improve 17??-ethinylestradiol desorption effect, which increased with the content of organic solvents, and the desorption degree of acetonitrile was higher than methanol.  相似文献   

14.
《Applied Geochemistry》2003,18(5):693-710
In experiments of 7 days duration using voltammetric and radiotracer measurement techniques, the role of different particle types in the sorption of dissolved metal species in a disturbed deep-sea bottom seawater system were investigated. Resuspension of oxic to suboxic surface sediment into the bottom water in the deep sea (either by natural events or industrial activities like Mn nodule mining) has been shown to be followed quickly by scavenging of dissolved heavy metals, e.g. released from interstitial water, on the resuspended particles. Compared to other deep-sea particles (like clay minerals, calcite and apatite), Mn and Fe oxides and oxyhydroxides were found to be by far the most important phases in scavenging many dissolved heavy metals. Only Pb was sorbed strongly on all particles used, with highest affinity to carbonate fluorapatite. Caesium+ was significantly scavenged only by clay minerals like illite. The sorption experiments support a simple electrostatic model: Hydrated cations and labile cationic chloro-complexes in seawater like Mn2+, MnCl+, Co2+, Ni2+, Cu2+, Zn2+, Ba2+, and PbCl+, are preferentially adsorbed or ion-exchanged on the negatively charged surfaces of Mn oxides. In contrast, oxyanions and neutrally or negatively charged complexes like HVO42−, MoO42−, HAsO42−, UO2(CO3)22−, and PbCO30 associate with neutral to slightly positive amphoteric Fe oxyhydroxide particles. Metals forming strong chloro-complexes in seawater like Cd (CdCl20), are less readily sorbed by oxides than others. A comparison of the results of voltammetric and radiotracer techniques revealed that after fast sorption within the first hour, isotopic exchange dominated reactions on MnO2-rich particles in the following days. This was especially pronounced for Mn and Co which are bound to the Mn oxide surface via a redox transformation.  相似文献   

15.
Cordierite has the ideal formula (Mg,Fe)2Al4Si5O18 .x(H2O,CO2), but it must contain some Fe3+ to account for its blue color and strong pleochroism. The site occupation and concentration of Fe3+ in two Mg-rich natural cordierites have been investigated by EPR and 57Fe Mössbauer spectroscopy. In addition, powder IR spectroscopy, X-ray diffraction, and TEM examination were used to characterize the samples. Single-crystal and powder EPR spectra indicate that Fe3+ is located on T11 in natural cordierites and not in the channels. The amount in Mg-rich cordierites is very small with an upper limit set by Mössbauer spectroscopy giving less than 0.004 cations per formula unit (pfu). Fe3+ in cordierite can, therefore, be considered insignificant for most petrologic calculations. Heat-treating cordierite in air at 1,000?°C for 2?days causes an oxidation and/or loss of Fe2+ on T11, together with an expulsion of Na+ from the channels, whereas heating at the Fe–FeO buffer produces little Fe3+ in cordierite. Heating at 1,000?°C removes all class I H2O, but small amounts of class II H2O remain as shown by the IR measurements. No evidence for channel Fe2+ or Fe3+ in the heat-treated samples was found. The blue color in cordierite arises from a broad absorption band (E//b and weaker with E//a) around 18,000?cm?1 originating from charge-transfer between Fe2+ in the octahedron and Fe3+ in the edge-shared T11 tetrahedron. It therefore appears that all natural cordierites contain some tetrahedral Fe3+. The brown color of samples heated in air may be due to the formation of very small amounts of submicroscopic magnetite and possibly hematite. These inclusions in cordierite can only be identified through TEM study.  相似文献   

16.
High water and organic content of sewage sludge constricts its reuse and disposal. It is often necessary to solidify/stabilize the dewatered sludge with solidifying agents before landfill disposal. In this study, the sewage sludge was conditioned with skeleton builders, i.e., fly ash and lime combined with ferric chloride for the purpose of improving the dewatering efficiency. The dewatered sewage sludge was then directly reused as landfill cover materials since the skeleton builders also play a role in solidification of sludge. The geotechnical properties of the dewatered sewage sludge were investigated. The results show that the plasticity index of the dewatered sludge increases compared to that of the dewatered sludge without any conditioner, and the permeability coefficient changes from 10?8 to 10?5 cm s?1. Furthermore, the strength of specimens increase with curing days. Microstructure analyses reveal that the main hydrated products are calcium silicate hydrate and ettringite, which contribute to the solidification/stabilization of the dewatered sludge. The results indicate that the dewatered sewage sludge conditioned with skeleton builders can be used as landfill covers. This study provides an alternative for traditional sewage sludge treatment and disposal.  相似文献   

17.
The dependence of the electronic and the crystallographic structure on temperature of synthetic Mnbearing ilvaites CaFe2+ 2-xMn2+ xFe3+ [Si2O7/O/OH] with 0≤x≤0.19 has been investigated. The change of the electronic structure was studied by 57Fe Mössbauer spectroscopy. The spectra show an increasing valence fluctuation rate between Fe2+ and Fe3+ in the double chain of edge-sharing octahedra with increasing temperature resulting in a mixed valent state of iron. The valence fluctuation rate is distinctly increased by the Mnsubstitution. The temperature of the crystallographic phase transition T x as studied by a high temperature Guinier method is distinctly lowered by the Mn-substitution (x = 0.0, T x=390K; x = 0.12, T x =370K; x = 0.19, T x=295K). The reasons for this behaviour are discussed in terms of Fe2 +, Fe3 + cation order-disorder, electronic relaxation rate, and relaxation of the lattice. In the monoclinic phase there is electron hopping between Fe2 +, Fe3 + pairs whereas in the orthorhombic phase there is extended electron delocalization via a narrow, d-band mechanism.  相似文献   

18.
In this study, sodium oxalate was employed to extract extracellular polymeric substances (EPS) from activated sludge samples. The optimum dose of sodium oxalate was 1.34 g/g VSS (volatile suspended solids), and the extraction time was 60 min at pH 7. The total EPS contents obtained under the optimized conditions were approximately 191 mg/g VSS, and they predominantly consisted of proteins, polysaccharides and humic substances. The extraction efficiencies of the chosen method for the major biopolymers were 39, 43 and 410 % higher compared with the ethylenediaminetetraacetic acid (EDTA), cation exchange resin and control methods. Cell lysis measured in terms of deoxyribonucleic acid, and unidentified EPS were approximately 50 % lower in the sodium oxalate method than in the NaOH and EDTA methods. The EPS composition and the ratio of proteins/polysaccharides (1.38–2.21) were extremely dependent on the operating conditions maintained during the extraction. The inductively coupled plasma spectroscopic results demonstrated that the release of divalent metals, such as Ca2+ and Mg2+, from the sludge matrix was directly correlated with higher EPS extraction efficiencies in the sodium oxalate protocol. Moreover, the precipitation of Ca2+ and Mg2+ as metallic oxalates disrupted the floc structure and subsequently enhanced the EPS recovery. Fourier transform infrared studies revealed the presence of functional groups due to EPS molecules in all extracted samples.  相似文献   

19.
Domain twinning of laihunite has been investigated based on diffracton phenomena, and its crystal structure has then been refined. Space group with respect to the domain isP21/c, and cell parametersa=5.813,b=4,812,c=10.211(A), β=90.87°. Atomic coordinate and bond length have been recalculated. Discussions are made of the Fe2+ distribution, lattice distortion, degree of order of laihunite and the relationship of this mineral with fayalite and ferrifayalite. The authors still hold that laih unite should be considered as a new silicate mineral with dominant Fe3+ and less amount of Fe2+.  相似文献   

20.
Voltaite is a mineral of fumaroles, solfatares, coal-fire gas vents, and acid-mine drainage systems. The nominal composition is K2Fe5 2+Fe3 3+Al(SO4)12·18H2O and the nominal symmetry is cubic, $Fd\overline{3}c$ . The tetragonal (I41/acd) superstructure of voltaite is known as the mineral pertlikite. In this study, we investigated 22 synthetic voltaite samples in which Fe2+ was partially or completely replaced by Mg, Zn, Mn, or Cd, by single-crystal and powder X-ray diffraction (both in-house and synchrotron). Two samples contained NH4 + instead of K+. The structure of voltaite is based on a framework defined by kröhnkite-like heteropolyhedral chains which host both M3+ and M2+ in octahedral coordination. Unit cell dimensions of the end-members scale almost linearly with the size of M2+. In the Fe2+-Mg-Zn solid solutions, the Fe2+-Mg and Fe2+-Zn solutions are linear (ideal) in terms of their lattice-parameter variations. The Mg-Zn solid solution, however, is strongly non-ideal. A detailed analysis of the topology of the chains showed that this behavior originates in expansion and contraction of individual M2+-O bonds within the chains. In the Mg-Zn solid solution, some of the M2+-O bonds expand while none contract. In the other solid solutions, expansion of some M2+-O bonds is always compensated by contraction of the other ones. Parts of the nominally cubic crystals are optically anisotropic and their symmetry is found to be tetragonal by single crystal X-ray diffraction measurements. The coexistence of cubic and tetragonal sectors within a single crystal without any detectable difference in their chemical composition is difficult to explain in terms of growth of such composite crystals. Mössbauer and infrared spectra collected on our synthetic crystals conform with previously published data.  相似文献   

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